1. Field of the Invention
This invention relates to a handling device for a power working machine, and in particular to a safety operation system of a handling device which is rotatably attached to the rear portion of a portable type power working machine such as a hedge trimmer.
2. The Prior Art
A portable-type power working machine, such as a hedge trimmer, is generally constituted by a prime mover case having a prime mover, such as an internal combustion engine or an electric motor, a mount base portion enclosing a transmission case having a power transmission device, such as gears, to be actuated by the prime mover, a working portion comprising clipper blades to be actuated via the aforementioned power transmission device by the prime mover, and a handling portion attached to the prime mover case or the mount base portion. This handling portion is constituted, for the convenience of manipulation thereof, by a front handle portion and a rear handle portion.
The rear handle portion is provided, for example, with a throttle lever for manipulating a throttle valve, for controlling an internal combustion engine employed as a prime mover, or with a power switch, for an electric motor. Moreover, the rear handle portion is rotatably mounted on the mount base so as to enable it to be effectively and easily operated against an object to be worked, and at the same time, adapted to be fastened at any suitable position with a fastening member.
Thus, in the operation of the foregoing portable-type power working machine, the rear handle portion is at first suitably rotated relative to the mount base, by taking the arrangement or position of the object to be worked into consideration, and then fastened at a desired position with the fastening member. Then, while the front handle portion is being held by one hand and the rear handle portion (fixed in a suitably rotated position) is being held by the other hand, the operation with the working portion such as clipper blades is performed while controlling the movement of the internal combustion engine by manipulating the control lever, such as the throttle lever, by the other hand holding the rear handle portion.
However, since the rear handle portion is rotatably mounted on the aforementioned portable-type power working machine, if the throttle lever is inadvertently manipulated while the rear handle portion is left in a rotatable condition, the working portion such as the clipper blades may be unexpectedly actuated due to an increase in the output of the engine. At the same time, the mount base to which the working portion is fixed may be caused to rotate relative to the rear handle portion, thus inviting an unexpected accident.
In an attempt to overcome this problem, there has been proposed a portable-type power working machine in U.S. Pat. No. 5,065,476, wherein the throttle lever is made impossible to manipulate as long as the rear handle is left rotatable. The portable-type power working machine proposed in this specification is provided with a releasable lock means comprising a projected portion-attached rotating lever and a recessed portion to be engaged with the projected portion. If the rear handle is desired to be rotated, the rotating lever is operated so as to disengage the projected portion from the recessed portion at first, and then the rear handle is rotated while keeping the projected portion in a disengaged state. Therefore, the handling of the rear handle portion is rather troublesome. Moreover, since the rotating lever is disposed below the rear handle portion due to the configurational restriction of the members of the rear handle portion as a whole, and, at the same time, since the rear handle portion is designed to be rotated while pushing the rotating lever, the rear handle portion is rendered difficult to manipulate.